Rotational isomeric state chains on a high coordination lattice: Dynamic Monte Carlo algorithm details

Clancy, Thomas C.; Mattice, Wayne L.

doi:10.1063/1.481640

Cited by 57 publications

(45 citation statements)

References 25 publications

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“…[64] The introduction of multiple-bead crankshaft-type Monte Carlo moves led to a significant acceleration for nonsymmetric potentials. [65] Meanwhile, the method has been extended to different topologies (diffusion of linear versus cyclic polyethylene), [66] geometries (polyethylene films rather than bulk) [67] and processes (structure formation upon cooling). [68] …”

Section: B)mentioning

confidence: 99%

Coarse-Graining in Polymer Simulation: From the Atomistic to the Mesoscopic Scale and Back

2002

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Polymers can be theoretically and computationally described by models pertaining to different length scales and corresponding time scales. These models have traditionally been used independently of each other. Recently, considerable progress has been made in systematically linking models of different scales. This Review focuses on the generation of lattice and off‐lattice coarse‐grained polymer models, whose “monomers” correspond to roughly a chemical repeat unit, from chemically detailed atomistic simulations of the same polymers. Computational methods are described as well as applications to polymers in the melt and in solution. The success of multiscale simulations in solving real‐world polymer problems that could not be solved in any other way suggests that they will have an important role to play in the future.

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Section: B)mentioning

confidence: 99%

Coarse-Graining in Polymer Simulation: From the Atomistic to the Mesoscopic Scale and Back

2002

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“…19 Normalizing over all 672 () 4 × 4 × 42) orientations on the high coordination lattice yields a perturbation which lowers the energy of the 2nd shell by ∼13.l9 kJ/mol in the case where the phenyl rings are pointing away from each other and increases the energy by ∼37.96 kJ/mol when the rings are pointed directly at each other. To invoke a neutral interaction for the former case, the perturbation is scaled by a factor of 0.87.…”

Section: Methodsmentioning

confidence: 99%

“…The coarse-grained 2nnd lattice method was applied in the same manner as done previously for polypropylene 12,19 and poly(vinyl chloride). 20 The local intrachain interactions were controlled by the rotational isomeric state model described by Yoon et al 21 for polystyrene, which was mapped onto the coarse-grained chains on a high coordination lattice.…”

Section: Methodsmentioning

confidence: 99%

Orientation of Phenyl Rings and Methylene Bisectors at the Free Surface of Atactic Polystyrene

et al. 2001

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Atomistically detailed models of free-standing thin films and the bulk structure of amorphous atactic polystyrene have been produced by reverse mapping from equilibrated coarse-grained models. The bridging technique employed in the simulation allows the generation of a moderate sized atomistic system (six independent parent chains of C 400 H 402 , 4812 atoms) with a more reasonable computational effort than is required when all of the construction is performed on chains expressed with atomistic detail. Reverse mapping from the coarsegrained model to the atomistically detailed model is found to be straightforward, without ring piercing or concatenation. The calculated surface energy (38 ( 10 erg/cm 2 ) is in reasonable agreement with prior experimental findings. The surface of the thin films is enriched in phenyl rings. The rings at the surface tend to be oriented so that they are pointing outward, but rings in the middle of the thin film show no preferred orientation. In contrast with the phenyl rings, the bisectors for the methylene groups show little tendency for orientation, even when the methylene groups are close to the surface. These observations in the simulation are in qualitative agreement with conclusions reported recently (Gautam et al. Phys. ReV. Lett. 2000, 30, 3854, and Briggman et al. J. Phys. Chem. B 2001, 105, 2785, based on the application of new spectroscopic techniques to the characterization of polymer surfaces.

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“…Equilibration uses single bead moves 37 and pivot moves of 2-6 beads. 38 A Monte Carlo step (MCS) is the length of the simulation that attempts one move, on an average, for each bead and each type of move.…”

Section: Methods and Simulation Detailsmentioning

confidence: 99%

Atomistic Simulation of Orientation of Methyl Groups and Methylene Bisectors, and Surface Segregation, in Freely Standing Thin Films of Atactic Poly(ethylene-co-propylene)

2004

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Atomistically detailed models of free-standing thin films of random poly(ethylene-co-propylene) were produced using a method recently applied to atactic polystyrene (Clancy, et al. J. Phys. Chem. B 2001, 105, 11493). Monte Carlo simulations of the copolymer were carried out at ethylene fractions that cover the entire range of composition investigated in a recent experimental work (Opdahl, et al. J. Phys. Chem. B 2002, 106, 5212) based on sum-frequency generation (SFG) spectroscopy. We find that there is a minor enrichment of methyl groups on the surface, as compared to the bulk composition. Interestingly, the orientation distribution of methyl and methylene units is not unimodal. For methyl units, there is about 50% probability of orientation perpendicular to the surface. The other 50% are randomly oriented. For the methylene bisector, the simulation shows that the distribution has two broad peaks at opposite angles (at 180°apart) to the surface normal. More conclusive results may be obtained by using larger sample sizes and analysis of a larger number of snapshots, both of which increase the computation time significantly. The opposite angle pairs nearly cancel each other in the computation of an average order parameter and give us a misleading net result that the bisectors are randomly oriented. With increasing ethylene fraction, the orientation distribution of methyl and methylene units tends to become more uniform; however, this change is small. The strong average orientation of methyl groups and weak average orientation of methylene groups is in agreement with experiments. However, the simulation does not show the significant relative increase in the surface methyl groups contributing to the SFG signal as compared to the bulk concentration or an increase in average orientation of methylene units, with an increase in the ethylene fraction, as inferred from the experimental results. We find that the raw experimental data obtained with an increase in ethylene fraction can be explained by the changes in the number of methyl and methylene groups on the surface rather than the increase in surface excess of the methyl groups contributing to the SFG signal, trans cancellation, and increase in orientation of methylene bisectors as deduced from the experiments.

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Rotational isomeric state chains on a high coordination lattice: Dynamic Monte Carlo algorithm details

Cited by 57 publications

References 25 publications

Coarse-Graining in Polymer Simulation: From the Atomistic to the Mesoscopic Scale and Back

Coarse-Graining in Polymer Simulation: From the Atomistic to the Mesoscopic Scale and Back

Orientation of Phenyl Rings and Methylene Bisectors at the Free Surface of Atactic Polystyrene

Atomistic Simulation of Orientation of Methyl Groups and Methylene Bisectors, and Surface Segregation, in Freely Standing Thin Films of Atactic Poly(ethylene-co-propylene)

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